1. Field of the Invention
The present invention relates to a technology for detecting whether an object has been subjected to drop impact or tilted.
2. Description of the Related Art
Goods including precision apparatuses are typically transported for long/short distances with various transportation media such as trucks, trains, ships. The goods may be damaged due to impact originating from inappropriate handling during the transport. Damage of the goods caused by impact of a predetermined level or smaller can be prevented by making a prior assessment on the goods accommodated in a package and taking a countermeasure against the damage based on a result of the assessment.
For example, Japanese Patent Application Laid-open No. 2001-108703 and Japanese Patent Application Laid-open No. 2001-199475 disclose conventional impact detecting apparatuses capable of detecting whether an object has been subjected to an impact. These conventional impact detecting apparatuses include a weight member having a flat surface to reflect an incoming light and a beam member that supports the weight member. The weight member is tilted upon receiving an impact. Therefore, by checking the current state of the weight member, it is possible to visually determine whether the object has been subjected to an impact during transportation.
Furthermore, NIPPON KAKO-KIZAI CO., LTD catalogue for “DROP SIGN” discloses another conventional impact detecting apparatus as shown in FIGS. 23A and 23B. The impact detecting apparatus includes a front case 1, a back case 2, leaf springs 3, a leaf-spring fixing member 4, guide plates 5, a weight 6, and window holes 7. When attached to an object in vertical posture, the impact detecting apparatus can detect impact that has been applied in the vertical direction. Specifically, in absence of an impact, the weight 6 is maintained by being sandwiched by the leaf springs 3 and an inner wall 8 in the center of a case formed of the front case 1 and the back case 2. However, when subjected to an impact, the weight 6 drops from the leaf springs 3. The weight 6 is colored so that when the weight 6 drops to a position corresponding to one of the window holes 7, a person can easily view the weight 6 through one of the window holes 7.
However, the impact detecting apparatuses disclosed in Japanese Patent Application Laid-open No. 2001-108703 and Japanese Patent Application Laid-open No. 2001-199457 have shortcomings. For example, they have a complicated structure, they cannot detect an impact both in a vertical direction and in a horizontal direction in a single event, and they detect only the first impact but cannot detect the second or later impacts.
On the other hand, in case of the impact detecting apparatus shown in FIG. 23A and FIG. 23B, the detection accuracy of an impact is unstable. More particularly, the impact detecting apparatus shown in FIG. 23B can be set to detect a plurality of detection levels. The same leaf springs 3 are shared for all the detection levels while the weight 6 having different mass is used depending on the detection levels. However, actual detection performance is not linked to the set detection levels as desired, so that the detection accuracy is often degraded. The reasons being that the lengths of the leaf springs 3 are relatively short with respect to the diameter of the weight 6. With such a configuration, a displacement amount “d” of the leaf springs 3 due to the movement of the weight 6 (see (3) of FIG. 23B) is relatively large, increasing a distance and time of contact between one of the leaf springs 3 and the weight 6. As a result, the leaf springs 3 are more likely to cause scoring on the weight 6. Furthermore, because the weight 6 is also supported by the inner wall 8, friction between the inner wall 8 and the weight 6 affects a dropping condition of the weight 6. Thus, even if the weight 6 and the leaf springs 3 are maintained in the same conditions, the same dropping condition cannot always be obtained.
Furthermore, in the impact detecting apparatus shown in FIGS. 23A and 23B, the weight 6 pushes the leaf springs 3 due to the force of an impact and drops by gravity, so that the weight 6 can drop only in a single direction. In other words, while an impact in the vertical direction can be detected, an impact in the horizontal direction cannot be detected. The impact in the horizontal direction is detectable if the impact detecting apparatus is mounted in horizontal posture. However, in this case, the impact in the vertical direction cannot be detected. Thus, to detect impact and tilt in both the vertical direction and in the horizontal direction in a single event, two impact detecting apparatuses need to be mounted on the object.
If the object (e.g., goods) receives an impact that is stronger than an expected level due to inappropriate handling or rough handling, it is difficult to completely prevent the goods from being damaged even with use of the above impact detecting apparatuses.
If a package accommodating the goods is remarkably damaged, damage of the goods may be detected through inspection before the goods is delivered to a customer or a shop. However, if the package is not damaged but only the goods in the package is damaged, the damage of the goods could be detected only after the goods is delivered to the customer or the shop, which leads to customer's complaint or reduction of customer's trust.